PURPOSE: To examine the incidence of mental disorders in children with cataract compared with children without cataract. DESIGN: Nationwide cohort study based on entries in comprehensive national databases. METHODS: The incidence of mental disorders in children born between 2000 and 2017 diagnosed with cataract before 10 years of age (n = 485) was compared with sex- and age-matched controls (n = 4358). Analyses were corrected to somatic disease in the child and parental socioeconomic status and psychiatric morbidity. The study was conducted as 2 university hospitals in Denmark managing children 6 years of age our younger with cataract. RESULTS: The incidence of mental disorders was nearly doubled in children with cataract compared with controls (odds ratio [OR], 1.83; 95% CI, 1.28–3.63). The risk of anxiety disorders was quadrupled (OR, 4.10; 95% CI, 1.90–8.84) and the risk of developmental delay was doubled (OR, 2.66; 95% CI, 1.45–4.90). The risk of mental disorders was significantly higher in children diagnosed with cataract in the first 3 years of life compared with controls (OR, 2.36; 95% CI, 1.53–3.64), whereas those diagnosed with cataract later in childhood did not have an increased risk (OR, 1.24; 95% CI, 0.66–2.30). CONCLUSIONS: The risk of mental disorders, in particular anxiety and neurodevelopmental delay, is markedly increased in children with cataract and even more so in those diagnosed within the first 3 years of life. Psychiatric screening instruments may be integrated in the management of these children.